Differences between EOS and Telos:
Governance and transparency:
EOS has a situation where Block One has over 10% of the token supply, is the sole core developer, and has an outsized influence on the system through this soft power and the reality of a >$1 billion US VC fund. They stay at arms length due to SEC concerns but are a strong shadow over all EOS governance. They telegraphed that they are proposing an all new constitution shortly.
Conversely on Telos, no group owns a percentage that large. The largest single TLOS token holder is GoodBlock and they have pledged the bulk of this (5 million TLOS) to a program called the GoodGrants which stakes the first year's NET and CPU resources to developers deploying apps on Telos for 1 year each as an incentive to developers.
Telos has a Telos Foundation with limited funds and no governance role which exists to promote the chain (publicity, conferences) and be liasons with exchanges, developers, and users.
Where the EOS 'Constitution' is greatly in doubt due to its initial vagueness and total lack of enforcement, Telos has an 'Operating Agreement' which is more clear and excplicit (and much longer). It has been generally praised for this. The Telos block producers have already demonstrated an ongoing vigiliance about enforcing their BP minimum requirements and rules. Many have been removed from the network for ignoring these (however far more have been able to easily meet them, showing that Telos is truly decentralized.)
Most importantly, Telos has built all the parts of EOS that were left out and are therefore currently failing to the point they risk being removed. Worker Proposals, Ratification, and Arbitration (with arbitrators elected in on-chain elections) are all built into Telos as strictly on-chain functions. EOS either lacks these altogether or has them as off-chain kludges.
Regarding software development:
Telos is largely interoperable with EOS in that any EOS program could be deployed on Telos needing no code changes. However, Telos has its own development team on top of what Block One releases and has added numerous features not available in EOS. First among these are robust voting features for any app and IPFS which is now in use and about to be expanded for all apps and users to use (on roadmap for about 8 weeks from now). So Telos apps can't go back to EOS and still use these improvements.
Telos allows both open source and proprietary code apps. EOS requires that all apps be open source in its constitution, yet so far has failed to ever enforce this. (Enforcement of anything seems impossible on EOS.)
Telos aims to be an onramp to EOSIO for apps coming from fee-based chains like Ethereum. To reduce the cost of deployment, the Telos Foundation offers RAM grants and GoodGrants offers 1 year's staking of all NET and CPU resources to allow apps to build a business before needing to pay for their resources. (1 TLOS token is worth 3-5 time 1 EOS tokens due to lower supply.)
Regarding Chain Rules:
Telos has a clear and explicit set of governance documents. There is very little guesswork. For example, the regproducer agreement for block producers lists not only prohibited actions, but also penalties for first and subsequent offences, the method of enforcement, and the requirement for other BPs to enforce. These rules are based in the idea that an advance understanding of precise rules allows people to better follow them (as opposed to broad principles that need a lot of interpretation).
Telos has elected arbitrators. So far the 9 candidates are all attorneys plus one expert in EOSIO lost key recovery. This is a system based in the idea that this form of blockchain governance and adjudication is the future of law. While there is base layer arbitration, it is clearly intended to be used with a light hand and requiring cryptographic proof for almost any arbitral judgement.
Regarding Funding and Partners:
Telos is an old-school crypto project, created by an international grassroots community of 130 contributors who worked together for 6 months. They were paid, in aggregate, ~5% of the chain's funds as a founders reward. Telos, by the way, has returned a greater percentage of value to EOS early supporters than any other chain. Telos = ~94%, EOS = 90%, Worbli = 36%, BOS = ~5%.
There is an on-chain elected board for the Telos Foundation (possibly the most comprehensive blockchain election on any chain to date - all actions are entirely on-chain and no off chain action is required to transfer power over multiple accounts and voting rights to the victors). However, this board only controls how to spend its funds on promotion of the chain. Beyond that, there is no company or central organization involved in Telos. Block One has no role, its tokens having been reduced from 100 million to 40,000 under the Telos genesis account cap.
More information can be read on the website.